Verbal Reasoning - Mental Ability Questions

It means that the first half of the alphabet is interchanged with second half of the alphabet. After making changes, nth letter from the left will be (n + 13)th letter of original series, ie English alphabet; If n is less than 14. But if n is more than 13, nth letter from left will be (n - 13)th letter from left.
In the given equation, we have to find out (13 - 7 =) 6th letter from right => (26 - 6 + 1 =) 21st letter from the left. Hence, required letter's position is more than 13; therefore the required letter is (21 - 13 =) 8th letter from left of original series, ie H.

It is irrelavent

Letters of the word PREMONITION are coded as follows:

Letters :  P    R    E    M    O    N    I    T    I    O    N

Code:        6    8    5    3    0    4    9    2    9    0    4

See the code below Is and Ns. Codes for I and N are 9 and 4 respectively. This indicates that the digits below each letters represent its code. Therefore, code for the word MONITOR is 3049208

We know that, ALpha and Omega are the first and last lettrs of in the Greek alphabet. Hence, alpha is to omega as first is to last.

Vaccines prevent diseases by developing immunity inside the body and vaccines must be given to children to build in them a resistance against diseases.